Commutator and method of making same



March 1, 1932. E. RAGAR 1,847,725

comlu'rA'roR mm um-non OF MAKING slum Filed July 20, 1929 COPPER RPLATED ATEU her.

. metallic particles float on the acid sothat as Patented Mar. 1,1932

UNITED STATES PATENT OFFICE,

ELMEIt BAGAR, or DAYTON, 01110, ASSIGNOVRY To nELco raonucrscoRPoRA'rIoN, or DAYTON, on o, A CORPORATION or DELAWARE COMMUTATOB. ANDMETHOD or MAKING sAiu:

Application filed July 20,

labor and material resulting in a reduction ofcost. 'It is well known tothose skilled in the art to secure the commutator segments which are i10 insulated from each other to a support by a body of phenolcondensation product which is molded so as to rigidly anchor thecommutator segments in a fixed relation withrespect to the commutatorsupporting mem- The commutator segments are usu ally cut or stamped froma strip of copper having the required cross sectional area. In theprocess of cutting or stamping the commutator segments from the strip,burrs are formed along the severed edges. If

these are not removed some of them. will flow in the plastic phenolcondensation prod- M uctduring the molding, which takes place .underextremely high pressure, so that some- I times a conducting path will beformedfrom one segment to another through the molded phenol condensationproduct. Whenever such a path is formed the commutator cannot be usedand is rejected. In order to over- 5 come this the commutator segmentsare rat-" tled in arevolvin drum whichknocks the burrs from the e ges.As the commutator segments are mixed with theiburrs which are oftentimes very finely divided metallic particles, they must be separated,which is usually done by submerging the commutator-segments in an acidwhich cuts gre ase and dirt on the segments and theoretically shoulddissolve the metallic particles. In practice, however, it has been foundthat finely divided the commutator segments are removed'from the acidthey necessarily'pass throughthese finely divided particles on thesurface thereby, defeating this treatment. 7

An object of this invention is to" overcome this short circuiting causedby the finely divided metallic particles flowing inthe phenolcondensation product. 11 This is accomplished by copper plating thecommutator'segments tator segments to have a trapezoidal face or 1929.Serial No. 379,697.

which fixes any loose metallic particles carried by the segments to thesegments, which prevents conducting paths being formed by.v the finemetallic particles flowing in the molding material while plastic.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of one form of the present e uinvention is clearly shown.

. In the drawings:

Fig. 1 is aside elevation looking in the direction or arrow 1 in Fig. 2.

Fig. 2 is a sectional view taken on the line 2 -2 of Fig. 1. Fig; 3 isaside view of the commutator segments. 7 s Y Fig. 4 is a view of theedge of a commutator segment, looking in the direction of arrow 4-.ofFig. 3.

Figs. 3 and 4 are drawn to a larger scale than Figs. 1 and 2. s

Fig.5 is a sectional view of the commutator showing the same clamped ina clamping block, the commutator being shown in a smaller scale thanFigs. 1 and 2. I A

In the drawings the reference character 10 indicates a copper commutatorsegment having the complementary tangs12 and 14 forming the edges ofasubstantially T-shaped sl-ot16.

Inthe drawings a radial face commutator has been shown-which requiresthe. commucrossgsectionalarea as best seen in Fig. 4.

-The commutator, segments 10 may be cut :01 stamped from a metal stripnotshown,

preferably copper, having a. trapezoidal I cross sectional area.- .Afterthe segments 10 a have :been severed from the strip of material theyare-placed in a tumbling drum where the burr is knocked from thecommutator segments so as to remove theburr and so as to leave asmoother edge. After the burr has been removed, the commutatorsegmentsare submerged in a bath of acid which cuts the grease and which shouldwash from I .the commutator segments the finely divided particles ofmetal removedin the tumbling drum. These finely divided particles ofmetal float on the surface of the acid so that as the commutatorsegments are lifted out of the acid they pass through this surfacethereby covering some of the segments 10 with metallic particles.

Instead of now assembling the commutator segments as is the usualpractice the commutator segments are copper plated after eing removedfrom the acid bath so as to fix the finely divided metallic'particles tothe commutator segments thereby preventing conducting paths from beingformed between the segments during the molding operation. i After the sements have been copper plated, these and pieces 11 of mica insulatingmaterial are assembled so to form an annulus which is placed in asuitable die so that the commutator segments may be molded in positionby a phenol condensation product forming the body 22, which has ananchor 24 engaging the slot 16 and which has an anchor QG'eXtending atright angles to the anchor 21, the anchor 26 engaging an annular recessprovided therefor in the iron support 28.

Intermediate the commutator segments 10 and the supporting member 28 ismounted a mica insulating annulus which insulates the copper segments10' from the support 28. It has been found that upon cooling after themolding operation the inner edges 32 of the commutator segments 10 havea tendency to inove away from the support 28 thereby failing to clampthe insulating segment 30 between the commutator segments '10 and thesupport 28. When this takes place the mica annulus 30 chips when therecess '31 of the commutator is reamed.

WVhenever the annulus 30 chips short circuits are often times formedbetween the commutator segments 10 and the support 28, this is anothersource of defective parts. In order to overcome this-chipping of thewasher 30 the commutator is held and the phenol condensation productreformed in a clamping block Ji l provided with a screw threaded member36 carrying a nut'38 that cooperates with a washer 80 to clamp anassembled commutator so as to re-form the phenol condensation product 22during the cooling of same. As is well known to those familiar with theart, phenol condensation does not have the same co-efficient ofexpansion as does metallic members 28 and 10. This being the case it canbe readily seen that even though the face of a commutator maybepractically flat when it comes out of the mold there will be a tendencyfor the commutator segments to warp during the cooling of the commutatorassembly. By placing the assembled commutator While hot into theclamping block QAyas' disclosed in Fig. 5, warping of the commutatorsegment 10 is prevented by washer or clamping member 40 being held inposition by the nut 38 carried by the screw member 36. As a result thephenol condensation product is re-formed during the cooling process.This is more fully disclosed in the copending application by Harper YV.Niswonger Serial No. 367,781, filed June 1, 1929, and assigned to thesame assignee.

In the disclosure a radial face commutator is shown. he copper platingof the commutator segments is not limited to commutator segments used inradial face commutator as its prineipl 's equally applicable to anycommutator segment and for that matteris not limited to commutatorsegments as it may be used to fix particles to any metallic body byelect-re plating.

lVhile the form of en'ibodiment of the present invention as hereindisclosed, constitutes a preferred form, it is to be understood thatother forms might be adopted, all. coming within the scope of the claimswhich follow.

V hat is claimed is as follows:

1'. A commutator comprising a plurality of radially arranged copperplated copper bars insulated from each other, each of said bars beingcomposed of con'iplementary tangs, said tangs being so positioned as toform a slot between them; an anchor of phenol condensation productextending between said tangs into the slot so as to hold the bars; asecond anchor extending at right angles to the firstanc'hor; a support,said support having an annular recess which lCCQlVQw said second anchorof said phenol condensation product whereby the commutator segments areheld in a relatively rigid relation with respect to said support.

2. The method of producing a commutator having a plurality of commutatorsegments insulated from each' othelgsaid commutator segments beingsupported on a support, com prising the steps of forming the commutatorsegments from a piece of copper; copper plating the formed commutatorsegments so as to fir: all looseparticles carried on the commutatorsegments 'tothe segments; assembling thec'opper plated commutator segments; and securing the assembled commutator segments to a supportingmember so as to hold theassembledcommutator segments in position.

The method of producing a commutator having a plurality of commutatorsegments insulated from each other-{said commutator segments beingsupported on'a support having a recess,'comprising the steps of formingthe commutator segments from a strip of materiah said commutatorsegments being formed with recesses; copper plat-ing the formedcommutator segments so as to secure all loose particles to the segments;assembling the commutator segments"; and securing the commutatorsegments to the support by molding phenol condensation product into saidrecesses in the segment and into said recess in the support.

4. The method of producing a commutator having a plurality of commutatorsegments insulated from each, said commutator segments being supportedon a support, comprising the steps of cutting commutator segments from astrip of copper; rattling the cut commutator segments in a tumbling drumto remove burr from the segments; copper plating the commutator segmentsso as to secure all loose particles carried by the commutator segmentsto the segments; and assembling the commutator segments and the supportprovided therefor.

5. The process of producing commutator segments comprising the steps offorming the commutator segments from a strip of copper and copperplating the copper segments so as to rigidly fix all loose copperparticles carmutator segments in a fixed relation Without Warping.

In testimony whereof I hereto aflix my sig nature.

ELMER RAGAR.

